This invention relates to a pressure cylinder which is longitudinally-slotted and sealed on both ends and, more specifically, this invention relates to a construction of such a cylinder wherein there is disposed a movable piston element whose work output is transmitted externally of the pressure cylinder in a radial manner as opposed to a linear manner from one end of the pressure cylinder.
Such rodless piston, or slotted pressure cylinders, as they are known in the industry, can more readily be applied to situations where size constraints render an end extending piston rod, of pressure cylinder arrangement, impractical. Mounting space that would typically be on the order of two times the stroke length can be reduced to the actual cylinder size when using a slotted pressure cylinder. Inherent in the construction of the slotted cylinder is the necessity to seal the bore in which the piston travels at the slot, while still providing external access along the stroke length of the piston. One such approach has been to provide a metallic, spring-acting strip over the slot and a piston with an outer flat portion which is slottedly engaged to the strip such that the piston assembly is guided along this strip. Such a slotted engagement between the piston and metallic seal has resulted in rapid wear of both the metallic strip seal and the piston assembly, and has further exhibited problems of smoothness of the movement of the piston assembly over the metallic strip seal.
Another existing slotted cylinder is disclosed in the European Patent EP-A 1-0069199, which uses a dual-sealing strip arrangement whereby a cover strip bearing on the outside wall of the cylinder is joined by a number of detachable connectors to an inner sealing strip bearing against the inner wall of the cylinder. As the piston and external actuating member travel along the slot, the detachable connectors on one side of the piston are detached and the connectors on the opposite side are joined. In order to guarantee a tight, secure, and removable connection between the cover and seal strips, a relatively expensive and complicated design of the actuator member and the two interlocking strips is necessary. Additionally, due to the constant joining and attaching of the two interlocking sealing strips, there is the undesirable effect of high wear on the components involved.
Still another slotted cylinder, disclosed by East German patent specification No. DD83708, discloses an elastic liner in the cylinder with the ends of the liner overlapping to form a seal at the longitudinal slot. The actuator member is connected to the piston in a nonradial manner, and extends through a slit in the liner and through the longitudinal slot. Such an arrangement has proven costly with regard to installation and maintenance time, and has further proven to be less than completely effective in sealing the cylinder bore.
Additionally, with the two above-mentioned flexible seal arrangements, it is required that the size of the specific seal to be used on a given size pressure cylinder be specifically matched, therefore requiring manufacturers to maintain large inventories of various size sealing elements.